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Emerging evidence suggests that zooplankton production is affected by physiological and nutritional constraints due to climate change and eutrophication, which in turn could have broad implications for food-web dynamics and fisheries production. In this study, we developed a resource-based zooplankton production dynamics model that causally links freshwater cladoceran and copepod daily production-to-biomass (P/B) ratios with water temperature, phytoplankton biomass and community composition, and zooplankton feeding selectivity. This model was used to evaluate constraints on zooplankton growth under four hypothetical scenarios: involving natural plankton community seasonal succession; lake fertilization to enhance fisheries production; eutrophication; and climatic warming. Our novel modeling approach predicts zooplankton production is strongly dependent on seasonal variation in resource availability and quality, which results in more complex zooplankton dynamics than predicted by simpler temperature-dependent models. For mesotrophic and hypereutrophic lakes, our study suggests that the ultimate control over zooplankton P/B ratios shifts from physiological control during colder periods to strong resource control during warmer periods. Our resource-based model provides important insights into the nature of biophysical control of zooplankton under a changing climate that has crucial implications for food web energy transfer and fisheries production. [ABSTRACT FROM AUTHOR]

Brett, M.R., 2021. How important is coastal tourism for island nations? An assessment of African and Indian Ocean islands. Journal of Coastal Research, 37(3), 568–575. Coconut Creek (Florida), ISSN 0749-0208. Coastal tourism is an important component of the global tourism industry, particularly for island nations where the tourism sector often exceeds 40% of gross domestic product. For African island and Indian Ocean island nations, the tourism sector's economic contribution has not received as much attention. This paper analyses the economic contribution of tourism to the economies of African island nations and analyzes tourism statistics from the World Travel and Tourism Council annual reports. Tourism is a major economic factor for the island nations and is concentrated in the coastal zone. The data indicates that islands with larger and more diversified economies performed better in terms of tourism receipts than did islands with less developed economies. The results show that the average per capita income on the islands is more than six-fold greater than the average for the African continent. To test the importance of the coastal zone, tourist infrastructure was mapped on two African island nations, Mauritius and the Seychelles. Given the predominance of tourist infrastructure in the coastal zone, and the importance of tourism to the economies of many of the African island nations, a rise in sea-level even of 0.5 to 1 meters poses a serious threat to the existence of these island nations. [ABSTRACT FROM AUTHOR]

The ecological success of shallow water reef-building corals has been linked to the symbiosis between the coral host and its dinoflagellate symbionts (herein ‘symbionts’). As mixotrophs, symbiotic corals depend on nutrients 1) transferred from their photosynthetic symbionts (autotrophy) and 2) acquired by host feeding on particulate organic resources (heterotrophy). However, coral species differ in the extent to which they depend on heterotrophy for nutrition and these differences are typically poorly defined. Here, a multi-tracer fatty acid approach was used to evaluate the trophic strategies of three species of common reef-building coral (Galaxea fascicularis, Pachyseris speciosa, and Pocillopora verrucosa) whose trophic strategies had previously been identified using carbon stable isotopes. The composition and various indices of fatty acids were compared to examine the relative contribution of symbiont autotrophy and host heterotrophy in coral energy acquisition. A linear discriminant analysis (LDA) was used to estimate the contribution of polyunsaturated fatty acids (PUFA) derived from various potential sources to the coral hosts. The total fatty acid composition and fatty acid indices revealed differences between the more heterotrophic (P. verrucosa) and more autotrophic (P. speciosa) coral hosts, with the coral host G. fascicularis showing overlap with the other two species and greater variability overall. For the more heterotrophic P. verrucosa, the fatty acid indices and LDA results both indicated a greater proportion of copepod-derived fatty acids compared to the other coral species. Overall, the LDA estimated that PUFA derived from particulate resources (e.g., copepods and diatoms) comprised a greater proportion of coral host PUFA in contrast to the lower proportion of symbiont-derived PUFA. These estimates provide insight into the importance of heterotrophy in coral nutrition, especially in productive reef systems. The study supports carbon stable isotope results and demonstrates the utility of fatty acid analyses for exploring the trophic strategies of reef-building corals. [ABSTRACT FROM AUTHOR]

Thin films with sinusoidally varying refractive index profiles display photonic band gap effects. Intentional deviations from the periodic index profile can be used to tailor the optical properties of the resulting thin film. We present experimental characterization of TiO2 films with periodic index profiles fabricated using a deposition technique known as glancing angle deposition (GLAD). The resulting porous thin films have a microstructure consisting of vertically aligned columns. Sinusoidal porosity gradients, and therefore sinusoidal index profiles, can be introduced in the direction of the substrate normal by fabricating columns with a periodically varying diameter. Local modifications of the index profile are achieved by inserting thin layers of constant porosity into the center of the film, or by discontinuously changing the phase of the sinusoidal gradient. The introduction of these structural defects creates a narrow optical passband inside the larger band gap, and we demonstrate how the properties of this passband can be controlled through modification of the defect parameters. The magnitude of the phase shift constituting the defect is shown to control the location of the resulting passband. By inserting a layer with in-plane birefringence, we show that it is possible to create two separate passbands, one for each polarization, within a single stop band. The results illustrate how nanoscale porosity engineering using GLAD is a precise technique for fabricating one-dimensionally periodic films with a variety of optical characteristics. [ABSTRACT FROM AUTHOR]

Oblique-incidence physical vapor deposition has been used to create optical thin films with a polygonal helix-shaped nanostructure. A series of titanium dioxide thin films are investigated, including triangle, square, pentagon, and star-shaped polygonal helices. Experimental optical measurements reveal a double-handed circular Bragg response: at one frequency band a polygonal helix reflects left-handed circularly polarized light, and at a second frequency band reflects right-handed circularly polarized light. The relative wavelength dependence of each reflection band is determined by the physical structure of the polygonal helix, a property that is set during the thin-film deposition process. Spectral-hole polarization filters, produced by adding twist and spacing layer defects to polygonal helix thin films, are also reported. [ABSTRACT FROM AUTHOR]

Disentangling the origin of species–genetic diversity correlations (SGDCs) is a challenging task that provides insight into the way that neutral and adaptive processes influence diversity at multiple levels. Genetic and species diversity are comprised by components that respond differently to the same ecological processes. Thus, it can be useful to partition species and genetic diversity into their different components to infer the mechanisms behind SGDCs. In this study, we applied such an approach using a high‐elevation Andean wetland system, where previous evidence identified neutral processes as major determinants of the strong and positive covariation between plant species richness and AFLP genetic diversity of the common sedge Carex gayana. To tease apart putative neutral and non‐neutral genetic variation of C. gayana, we identified loci putatively under selection from a dataset of 1,709 SNPs produced using restriction site‐associated DNA sequencing (RAD‐seq). Significant and positive relationships between local estimates of genetic and species diversities (α‐SGDCs) were only found with the putatively neutral loci datasets and with species richness, confirming that neutral processes were primarily driving the correlations and that the involved processes differentially influenced local species diversity components (i.e., richness and evenness). In contrast, SGDCs based on genetic and community dissimilarities (β‐SGDCs) were only significant with the putative non‐neutral datasets. This suggests that selective processes influencing C. gayana genetic diversity were involved in the detected correlations. Together, our results demonstrate that analyzing distinct components of genetic and species diversity simultaneously is useful to determine the mechanisms behind species–genetic diversity relationships. This study uses a dataset of 1,709 single nucleotide polymorphisms (SNP) to compare species–genetic diversity correlations (SGDCs) between plant species diversity of high Andean wetlands and putatively neutral and non‐neutral genetic diversity of the plant Carex gayana. We found contrasting SGDC patterns between the putatively neutral and non‐neutral SNP loci, and that C. gayana SNP genetic diversity was conspicuously low in some wetlands compared to previously reported AFLP genetic diversity and species diversity estimates. Our results indicate that SNPs are well‐suited genetic markers for SGDC studies. [ABSTRACT FROM AUTHOR]

The U.S. president may act unilaterally in issuing executive orders within the office's inherent powers. To date, no cross‐time study has explored the relationship of his doing so with subsequent observed approval ratings. We do so here and estimate the relationship between the president's issuing of executive orders and subsequent job approval ratings at the aggregate level. While structural factors continue to explain long‐run approval rates, the president's use of unilateral powers also is associated through time with those rates, even when controlling for external factors such as wars and scandals. Thus, while some researchers may suspect that executive orders may undermine long‐term confidence in the institution of the presidency, we find that such uses of unilateral power may conditionally lead to gains in long‐term public opinion of the president. [ABSTRACT FROM AUTHOR]

Mixing models have become requisite tools for analyzing biotracer data, most commonly stable isotope ratios, to infer dietary contributions of multiple sources to a consumer. However, Bayesian mixing models will always return a result that defaults to their priors if the data poorly resolve the source contributions, and thus, their interpretation requires caution. We describe an application of information theory to quantify how much has been learned about a consumer’s diet from new biotracer data. We apply the approach to two example data sets. We find that variation in the isotope ratios of sources limits the precision of estimates for the consumer’s diet, even with a large number of consumer samples. Thus, the approach which we describe is a type of power analysis that uses a priori simulations to find an optimal sample size. Biotracer data are fundamentally limited in their ability to discriminate consumer diets. We suggest that other types of data, such as gut content analysis, must be used as prior information in model fitting, to improve model learning about the consumer’s diet. Information theory may also be used to identify optimal sampling protocols in situations where sampling of consumers is limited due to expense or ethical concerns. [ABSTRACT FROM AUTHOR]

Abstract: The deuterium ratio (2H/1H) in tissue is often used to estimate terrestrial subsidies to aquatic consumers because of strongly differentiated values between terrestrial and aquatic primary producers. However, quantitative deuterium‐based analyses of terrestrial resource assimilation are highly dependent on several poorly defined assumptions. We explored the sensitivity of these estimates to assumptions regarding environmental water contributions to consumer deuterium content (ω) and algal photosynthetic hydrogen discrimination (εH). We also tested whether 13C/12C and 2H/1H‐based estimates of terrestrial resource assimilation give similar outcomes. The average of the 12 experiments that have directly estimated proportional contributions of environmental water to consumer tissue 2H/1H was 0.27 ± 0.11 (mean ± SD), with similar values for invertebrates and fish. Conversely, of the 28 field studies that have used 2H/1H to characterize aquatic food webs, all but one assume a value that is less than our current best estimate, usually substantially less. A reanalysis of the raw data from four recent case studies indicates the calculated terrestrial contribution to aquatic consumers is extremely sensitive to this assumption. When the authors’ original assumptions were used (i.e., ω = 0.16 ± 0.05), the estimated proportional contribution of terrestrial resources to aquatic consumers (θT) averaged 29 ± 17%, and when ω = 0.27 was used the average estimated assimilation of allochthonous resources was ≈0.00. A compilation of published photosynthetic hydrogen discrimination values for microalgae averaged εH = −150 ± 27‰ (SD, n = 99), and a sensitivity analysis showed the outcomes of these calculations were also strongly influenced by uncertainty in εH. There was no statistical association between 13C/12C and 2H/1H‐based estimates of terrestrial subsidies (r = −0.12, n = 274). This analysis indicates that the assumptions in deuterium‐based estimates of terrestrial resource assimilation are highly influential but poorly constrained; therefore, the impact of these assumptions on calculated outputs must be carefully assessed and thoroughly reported. Due to the highly uncertain assumptions inherent in deuterium‐based analyses, we urge much more caution when using this approach to estimate terrestrial subsidies to consumers in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Understanding which factors affect the algal bioavailability of dissolved organic nitrogen (DON) compounds in natural surface waters is important for our understanding of nutrient biogeochemistry and water quality management. We used nitrogen uptake kinetics and algal cell yield to characterize the algal bioavailability of 22 dissolved DON compounds that are commonly found in natural surface waters and wastewater treatment plant effluents, including urea, amino acids, amino sugars, nucleotides, pyrimidines, oraganonitriles, polyacrylamide, EDTA, caffeine, phenolic compounds and humic acids. Twelve of these compounds were highly bioavailable, including urea, dissolved free amino acids, bovine serum albumin, DNA, RNA, ATP, AMP, acetonitrile and caffeine. Four compounds had intermediate bioavailability including two humic acids (Elliott Soil and Pahokee Peat), glycylglycine, RNA and uracil. The remaining six compounds were classified as recalcitrant, i.e., EDTA, 2,3-Dinitrophenol, aminobenzoic acid, polyacrylamide and Aldrich humic acid. For many of the compounds tested, the algal cell yield was only 60–80% of expected relative to DON uptake. These results help explain why some DON compounds are more likely to persist in natural systems, and why the DON pool is often recalcitrant in surface waters. [ABSTRACT FROM AUTHOR]

Glancing angle deposition is used to create porous liquid crystal alignment layers with high aspect-ratio, three-dimensional features. We use solid-state deuterium nuclear magnetic resonance to determine the alignment of alpha deuterated 4′-pentyl-4-cyanobiphenyl in a 3.2 μm thick SiO2 film comprised of independent, helical structures. Comparing measured spectra with models, we determine that the liquid crystalline molecules exhibit chiral ordering dictated by the features of the template films. In the plane of deposition the liquid crystalline molecules tilt away from the substrate normal at an average angle of 51°, which is commensurate with the helical features of the chiral template. [ABSTRACT FROM AUTHOR]

Organisms at the base of stream food webs are typically poor in long‐chain polyunsaturated fatty acids (LC‐PUFA), especially in docosahexaenoic acid (DHA), whereas consumers at higher trophic levels are often rich in LC‐PUFA. For example, fish tissues, especially the brain, are DHA‐rich. This obvious mismatch between consumer LC‐PUFA and their basal dietary supply may result from selective retention and/or endogenous conversion of dietary precursors to LC‐PUFA.To determine which is more likely, we investigated compound‐specific carbon stable isotopes in PUFA (δ13CPUFA) of potential basal resources (stream epilithon, leaf litter) and consumers (invertebrates, European bullhead, and two salmonid species and their brain, eye, liver, and muscle tissues). We predicted that consumer‐PUFA, depleted in 13C values relative to their dietary sources, would indicate internal de novo PUFA synthesis. Alternatively, higher consumer‐δ13CPUFA values would imply selective retention of aquatic (epilithon and conditioned leaves) rather than terrestrial resources or internal production, irrespective of trophic levels.Invertebrate grazers and predators resembled δ13C values of essential fatty acids (δ13CEFA) of benthic algae, while shredder‐δ13CEFA values reflected those of conditioned rather than fresh leaves. Lower eye‐δ13CEFA values of salmonids than in livers indicated high retention of dietary PUFA sources (invertebrates and epilithon). Stable isotope values of eicosapentaenoic acid suggest that all consumers retained algal EPA, while insectivorous fish produced DHA in their liver. There is no further evidence from carbon stable isotopes for local PUFA conversion within neural tissues.Our study demonstrates that δ13CPUFA can be used to track sources of these highly functional molecules in aquatic consumers and highlights the importance of algal derived‐PUFA for these consumers in oligotrophic headwater streams. [ABSTRACT FROM AUTHOR]

Many freshwater systems receive substantial inputs of terrestrial organic matter. Terrestrially derived dissolved organic carbon (t-DOC) inputs can modify light availability, the spatial distribution of primary production, heat, and oxygen in aquatic systems, as well as inorganic nutrient bioavailability. It is also well-established that some terrestrial inputs (such as invertebrates and fruits) provide high-quality food resources for consumers in some systems., In small to moderate-sized streams, leaf litter inputs average approximately three times greater than the autochthonous production. Conversely, in oligo/mesotrophic lakes algal production is typically five times greater than the available flux of allochthonous basal resources., Terrestrial particulate organic carbon (t-POC) inputs to lakes and rivers are comprised of 80%-90% biochemically recalcitrant lignocellulose, which is highly resistant to enzymatic breakdown by animal consumers. Further, t-POC and heterotrophic bacteria lack essential biochemical compounds that are critical for rapid growth and reproduction in aquatic invertebrates and fishes. Several studies have directly shown that these resources have very low food quality for herbivorous zooplankton and benthic invertebrates., Much of the nitrogen assimilated by stream consumers is probably of algal origin, even in systems where there appears to be a significant terrestrial carbon contribution. Amino acid stable isotope analyses for large river food webs indicate that most upper trophic level essential amino acids are derived from algae. Similarly, profiles of essential fatty acids in consumers show a strong dependence on the algal food resources., Primary production to respiration ratios are not a meaningful index to assess consumer allochthony because respiration represents an oxidised carbon flux that cannot be utilised by animal consumers. Rather, the relative importance of allochthonous subsidies for upper trophic level production should be addressed by considering the rates at which terrestrial and autochthonous resources are consumed and the growth efficiency supported by this food., Ultimately, the biochemical composition of a particular basal resource, and not just its quantity or origin, determines how readily this material is incorporated into upper trophic level consumers. Because of its highly favourable biochemical composition and greater availability, we conclude that microalgal production supports most animal production in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Given the importance of the watershed protection plans, direct determination of phosphorus (P) mineralization rates in advanced wastewater treatment facility effluents is crucial for developing the most protective strategies minimiz eutrophication in receiving surface waters. In this study, algal bioassays were used to determine the uptake rate of dissolved P in effluents from a broad range of advanced nutrient removal technologies (e.g., membrane biological reactor, traditional biological, tertiary membrane, Blue PRO™, etc.). Dissolved P uptake kinetics were fit to a gamma model and three first-order decay models. A traditional one-pool model correlated poorly with the experimental data (i.e., r 2 = 0.73 ± 0.09), whereas two-pool model and three-pool models performed much better (i.e., r 2 > 0.9). These models also provided strong evidence for the existence of recalcitrant P in the effluents from these tertiary facilities. The Gamma model showed the mineralization of organic P followed a reactive continuum and further suggested the partitioning of P loads with different bioavailability levels should be accounted for the future modeling practices. From a modeling perspective, the Gamma model should be considered to be the theoretically best model as it gave the most parsimonious fit to the data using the fewest terms. Our study suggested that the current Total Maximum Daily Load (TMDL) model could be easily modified with the updated mineralization kinetics, which should lead to both ecological and economic benefits. [ABSTRACT FROM AUTHOR]

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a ‘consumer-resource library’ of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This library corresponds to the resource or producer file in classic Bayesian mixing models such as MixSIR or SIAR. Because this library is based on the FA profiles of zooplankton consuming known diets, and not the FA profiles of algae directly, trophic modification of consumer lipids is directly accounted for. To test the model, we simulated hypothetical Daphnia comprised of 80% diatoms, 10% green algae, and 10% cryptophytes and compared the FA signatures of these known pseudo-mixtures to outputs generated by the mixing model. The algorithm inferred these simulated consumers were comprised of 82% (63-92%) [median (2.5th to 97.5th percentile credible interval)] diatoms, 11% (4-22%) green algae, and 6% (0-25%) cryptophytes. We used the same model with published phytoplankton stable isotope (SI) data for δ13C and δ15N to examine how a SI based approach resolved a similar scenario. With SI, the algorithm inferred that the simulated consumer assimilated 52% (4-91%) diatoms, 23% (1-78%) green algae, and 18% (1-73%) cyanobacteria. The accuracy and precision of SI based estimates was extremely sensitive to both resource and consumer uncertainty, as well as the trophic fractionation assumption. These results indicate that when using only two tracers with substantial uncertainty for the putative resources, as is often the case in this class of analyses, the underdetermined constraint in consumer-resource SI analyses may be intractable. The FA based approach alleviated the underdetermined constraint because many more FA biomarkers were utilized (n < 20), different primary producers (e.g., diatoms, green algae, and cryptophytes) have very characteristic FA compositions, and the FA profiles of many aquatic primary consumers are strongly influenced by their diets. [ABSTRACT FROM AUTHOR]

Over a period of some forty years, 380/990–421/1030, the Fatimids in Egypt exchanged embassies with their Zirid viceroys in Ifrīqiya after these had been recognized as a hereditary dynasty, and to a lesser extent with their Kalbid deputies in Sicily. Sijillāt or official letters of the Fatimid chancery, accompanied by sumptuous presents, invested the Zirids with their authority and favoured them with important announcements, while the Zirids replied in kind. The embassies were ostentatiously welcomed by the Zirids as proof of their legitimacy, while serving to maintain the connection with Cairo on which the Fatimids were similarly dependent for the sake of their imperial standing in the world. The importance of that connection to both dynasties was shown in the 440s/1050s, when it was broken by the Zirids and restored by a Fatimid intervention, celebrated in a fresh series of sijillāt. With their emphasis on the style as much as the substance of the messages, the exchanges are excellent illustrations of mediaeval diplomatic correspondence as described by John Wansbrough in Lingua Franca in the Mediterranean. [ABSTRACT FROM PUBLISHER]

There is considerable interest in the pathways by which carbon and growth-limiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant-animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrestrial organic matter are potential trophic resources for Zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) and intermediate-quality (Chlcimydomonas sp. and Scenedesmus gracilis) phytoplankton species, two heterotrophic bacterial strains, and particles from the globally dispersed riparian grass, Pliragmites australis, representing terrestrial particulate organic carbon (t-POC). We also fed Daplmia with various mixed diets, and compared Daphnia fatty acid, carbon, and nitrogen assimilation across treatments. Our results suggest that bacteria were nutritionally inadequate diets because they lacked sterols and polyunsaturated omega-3 and omega-6 (CÜ-3 and co-6) fatty acids (PUFAs). However, Daplmia were able to effectively use carbon and nitrogen from Actinobacteria, if their basal needs for essential fatty acids and sterols were met by phytoplankton. In contrast to bacteria, t-POC contained sterols and co-6 and co-3 fatty acids, but only at 22%, 1.4%, and 0.2% of phytoplankton levels, respectively, which indicated that t-POC food quality was especially restricted with regard to co-3 PUFAs. Our results also showed higher assimilation of carbon than fatty acids from t-POC and bacteria into Daphnia, based on stable-isotope and fatty acids analysis, respectively. A relatively high (>20%) assimilation of carbon and fatty acids from t-POC was observed only when the proportion of t-POC was >60%, but due to low PUFA to carbon ratio, these conditions yielded poor Daphnia growth. Because of lower assimilation for carbon, nitrogen, and fatty acids from t-POC relative to diets of bacteria mixed with phytoplankton, we conclude that the microbial food web, supported by phytoplankton, and not direct t-POC consumption, may support Zooplankton production. Our results suggest that terrestrial particulate organic carbon poorly supports upper trophic levels of the lakes. [ABSTRACT FROM AUTHOR]

We explored how dietary bacteria affect the life history traits and biochemical composition of Daphnia magna, using three bacteria taxa with very different lipid composition. Our objectives were to (1) examine whether and how bacteria-dominated diets affect Daphnia survival, growth, and fecundity, (2) see whether bacteria-specific fatty acid ( FA) biomarkers accrued in Daphnia lipids, and (3) explore the quantitative relationship between bacteria availability in Daphnia diets and the amounts of bacterial FA in their lipids. Daphnia were fed monospecific and mixed diets of heterotrophic ( Micrococcus luteus) or methanotrophic bacteria ( Methylomonas methanica and Methylosinus trichosporium) and two phytoplankton species ( Cryptomonas ozolinii and Scenedesmus obliquus). Daphnia neonates fed pure bacteria diets died after 6-12 days and produced no viable offspring, whereas those fed pure phytoplankton diets had high survival, growth, and reproduction success. Daphnia fed a mixed diet with 80% M. luteus and 20% of either phytoplankton had high somatic growth, but low reproduction. Conversely, Daphnia fed mixed diets including 80% of either methane-oxidizing bacteria and 20% Cryptomonas had high reproduction rates, but low somatic growth. All Daphnia fed mixed bacteria and phytoplankton diets had strong evidence of both bacteria- and phytoplankton-specific FA biomarkers in their lipids. FA mixing model calculations indicated that Daphnia that received 80% of their carbon from bacteria assimilated 46 ± 25% of their FA from this source. A bacteria-phytoplankton gradient experiment showed a strong positive correlation between the proportions of the bacterial FA in the Daphnia and their diet, indicating that bacterial utilization can be traced in this keystone consumer using FA biomarkers. [ABSTRACT FROM AUTHOR]

We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure. [ABSTRACT FROM AUTHOR]

Many studies have concluded terrestrial carbon inputs contribute 20-70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. We conducted a quantitative analysis of terrestrial carbon mass influx and algal primary production estimates for oligo/mesotrophic lakes (i.e., TP≤20 μg L-1). In keeping with the principle of mass conservation, only the flux of terrestrial carbon retained within lakes can be utilized by zooplankton. Our field data compilation showed the median (interquartile range) terrestrial particulate organic carbon (t-POC), available dissolved organic carbon (t-DOC) inputs, and in-lake bacterial and algal production were 11 (8-17), 34 (11-78), 74 (37-165), and 253 (115-546) mg C m-2 d-1, respectively. Despite the widespread view that terrestrial inputs dominate the carbon flux of many lakes, our analysis indicates algal production is a factor 4-7 greater than the available flux of allochthonous basal resources in low productivity lakes. Lakes with high loading of t-DOC also have high hydraulic flushing rates. Because t-DOC is processed, i.e., mineralized or lost to the sediments, in lakes at ≈0.1% d-1, in systems with the highest t-DOC inputs (i.e., 1000 mg m-2 d-1) a median of 98% of the t-DOC flux is advected and therefore is not available to support zooplankton production. Further, advection is the primary fate of t-DOC in lakes with hydraulic retention times <3 years. When taking into account the availability and quality of terrestrial and autochthonous fluxes, this analysis indicates ≈95-99% of aquatic herbivore production is supported by in-lake primary production. [ABSTRACT FROM AUTHOR]

Abstract: Because eutrophication is a widespread consequence of wastewater discharges, there is a strong impetus to develop new approaches to remove phosphorus (P) from wastewater treatment plant (WWTP) effluents. We examined the effluents from a pilot plant that is testing various alum based processes for achieving>99% P removal, however, it is not known how these advanced P removal technologies affect the bioavailability of P (BAP). We tested how the percent BAP (%BAP) varied with different P removal levels using an algal growth bioassay methodology. This facility reduced total P concentrations from ≈ 500μgL−1 in the pilot plant influent to 19±4 (±SD)μgL−1 in the final effluent, and our results showed that as the level of P removal increased, the %BAP of the product declined sharply, r 2 =0.98. Prior to alum treatment, the influent had an average %BAP of 79±13%, and after three steps of alum-based removal the %BAP averaged 7±4%. Thus, this alum based P removal process was very effective at sequestering the P forms that most readily stimulate algal growth. Further, our results show the final BAP of the effluent was only ≈ 50% of the “reactive” P concentration. These results have important implications for nutrient management and trading schemes. [Copyright &y& Elsevier]

Hood Canal, Washington, USA, is a poorly ventilated fjord-like sub-basin of Puget Sound that commonly experiences hypoxia. This study examined the influence of watershed soils, vegetation, physical features, and population density on nitrogen (N) export to Hood Canal from 43 tributaries. We also linked our watershed study to the estuary using a salinity mass balance model that calculated the relative magnitude of N loading to Hood Canal from watershed, direct precipitation, and marine sources. The overall flow-weighted total dissolved N (TDN) and particulate N input concentrations to Hood Canal were 152 and 49 μg l, respectively. Nitrate and dissolved organic N comprised 64 and 29% of TDN, respectively. The optimal regression models for TDN concentration and areal yield included a land cover term suggesting an effect of N-fixing red alder ( Alnus rubra) and a human population density term (suggesting onsite septic system (OSS) discharges). There was pronounced seasonality in stream water TDN concentrations, particularly for catchments with a high prevalence of red alder, with the lowest concentrations occurring in the summer and the highest occurring in November-December. Due to strong seasonality in TDN concentrations and in particular stream flow, over 60% of the TDN export from this watershed occurred during the 3 month period of November-January. Entrainment of marine water into the surface layer of Hood Canal accounted for ≈98% of N loading to the euphotic zone of this estuary, and in a worst case scenario OSS N inputs contribute ≈0.5% of total N loading. Domestic wastewater discharges and red alders appear to be a very important N source for many streams, but a minor nutrient source for the estuary as a whole. [ABSTRACT FROM AUTHOR]

1. Analyses of zooplankton fatty acid (FA) composition in laboratory experiments and samples collected from lakes in New Zealand spanning a wide gradient of productivity were used to assess the extent to which FAs might infer their diet. We used the cladocerans, Daphnia and Ceriodaphnia, and the calanoid copepod, Boeckella, as test organisms, and monocultures of cryptophytes, chlorophytes and cyanobacteria as food. Based on reproductive success, cryptophytes were the highest food quality, chlorophytes were intermediate and cyanobacteria the poorest. 2. Several FA groups were highly correlated between zooplankton and their diets. They were monounsaturated fatty acids (MUFAs), and ω3 and ω6 polyunsaturated fatty acids (PUFAs) for cladocerans, and saturated fatty acids (SAFAs) and ω3 PUFAs for copepods. Several FAs varied significantly less in the zooplankton than in their monoculture diets, e.g. MUFAs in Daphnia, and ω3 and ω6 PUFAs in Ceriodaphnia, despite clear dietary dependency for these FAs. 3. Zooplankton collected from lakes in New Zealand had more eicosapentaenoic acid (EPA) ( Daphnia), more highly unsaturated ω3 and ω6 FAs (C, C; Daphnia, Ceriodaphnia, Boeckella) and less ω3 C PUFAs ( Daphnia, Ceriodaphnia, Boeckella) and ω6 C PUFAs ( Daphnia, Ceriodaphnia) than measured in the same species reared on phytoplankton in the laboratory. 4. Analyses of FA composition of seston and freshwater zooplankton globally showed that, in general, zooplankton had a significantly higher proportion of arachidonic acid and EPA than seston, and copepods also had a higher percentage of docosahexaenoic acid than seston. 5. These results suggest that zooplankton selectively incorporate the most physiologically important FAs. This could be a consequence of preferential assimilation, selective feeding on more nutritious cells or locating and feeding within higher food quality food patches. [ABSTRACT FROM AUTHOR]

We collected suspended particulate matter (seston) and zooplankton samples from Lake Washington in Seattle, Washington, USA, over a 10-month period to investigate the effects of food availability on zooplankton fatty acid (FA) composition. The percentage of nutritionally critical ω3 polyunsaturated fatty acids (PUFA) in the seston varied from 8% of the FA pool in midsummer to 30% during the spring diatom bloom. Zooplankton accumulated much higher percentages ω3 PUFA than was available in the seston. In particular, cladocerans preferentially accumulated eicosapentaenoic acid (EPA, 20:5ω3), copepods accumulated docosahexaenoic acid (DHA, 22:6ω3), and both copepods and cladocerans accumulated 18 carbon chain ω3 PUFAs (C18 ω3). By comparison, the FA of zooplanktivorous juvenile sockeye salmon (Oncorhynchus nerka) were strongly dominated by EPA (12.5% ± 2.1%) and DHA (28.2% ± 8.7%). The saturated fatty acid and the arachidonic acid (ARA, 20:4ω6) composition of Diaptomus ashlandi was strongly (r2 = 0.76) and moderately (r2 0.54) correlated with the prevalence of these FAs in the seston. Furthermore, the DHA content of Diaptomus was moderately correlated with the seston's DHA content (r2 = 0.45) and very strongly correlated with seston EPA (r2 = 0.89). Since EPA was the most prevalent PUFA in the seston and DHA was the most prevalent PUFA in Diaptomus, these results suggest that Diaptomus may synthesize DHA from the EPA in their food. In general, zooplankton species in Lake Washington were strongly enriched with those FA molecules that are most physiologically important for fish nutrition (i.e., ARA, EPA, and DHA), indicating a clear mechanism by which changes in seston composition influence fisheries ecology. [ABSTRACT FROM AUTHOR]

Terrestrial organic matter inputs have long been thought to play an important role in aquatic food web dynamics. Results from recent whole lake 13C addition experiments suggest terrestrial particulate organic carbon (t-POC) inputs account for a disproportionate portion of zooplankton production. For example, several studies concluded that although t-POC only represented ≈20% of the flux of particulate carbon available to herbivorous zooplankton, this food source accounted for ≈50% of the C incorporated by zooplankton. We tested the direct dietary impact of t-POC (from the leaves of riparian vegetation) and various phytoplankton on Daphnia magna somatic growth, reproduction, growth efficiency, and lipid composition. By itself, t-POC was a very poor quality resource compared to cryptophytes, diatoms, and chlorophytes, but t-POC had similar food quality compared to cyanobacteria. Small additions of high quality Cryptomonas ozolinii to t-POC-dominated diets greatly increased Daphnia growth and reproduction. When offered alone, t-POC resulted in a Daphnia growth efficiency of 5 ± 1%, whereas 100% Cryptomonas and Scenedesmus obliquus diets resulted in growth efficiencies of 46 ± 8% (± SD) and 36 ± 3%. respectively. When offered in a 50:50 mixed diet with Cryptomonas or Scenedesmus, the t-POC fraction resulted in a partial growth efficiency of 22 ± 9% and 15 ± 6%, respectively. Daphnia that obtained 80% of their available food from t-POC assimilated 84% of their fatty acids from the phytoplankton component of their diet. Overall, our results suggest Daphnia selectively allocate phytoplankton-derived POC and lipids to enhance somatic growth and reproduction, while t-POC makes a minor contribution to zooplankton production. [ABSTRACT FROM AUTHOR]

Abstract: Ultrathin layer chromatography (UTLC) is a relatively new variant of thin layer chromatography, with a 10 m thick monolithic silica sorbent layer that gives faster separations with lower limits of detection and reduced analyte and solvent volumes. We have produced UTLC plates with controllable nanostructure and thickness, and show that the layer separation characteristics depends on the film nanostructure. We also show that layers made with in-plane anisotropic nanostructures will exhibit a decoupling effect, where the analyte spots do not develop in the same direction as the solvent front movement. The added layer morphology and material selection adds a degree of freedom to UTLC, and may have applications in multi-dimensional TLC. [Copyright &y& Elsevier]

1. We conducted a statistical reassessment of data previously reported in the lake total phosphorus (TP) input/output literature ( n = 305) to determine which lake characteristics are most strongly associated with lake phosphorus concentration and retention. We tested five different hypotheses for predicting lake TP concentrations and phosphorus retention. 2. The Vollenweider phosphorus mass loading model can be expressed as: TPout = TPin/(1 + σ τw), where TPin is the flow-weighted input TP concentration, τw is the lake hydraulic retention time and σ is a first-order rate constant for phosphorus loss. 3. The inflow-weighted TP input concentration is a moderately strong predictor ( r2 = 0.71) of lake phosphorus concentrations when using log–log transformed data. Lake TP retention is negatively correlated with lake hydraulic retention time ( r2 = 0.35). 4. Of the approaches tested, the best fit to observed data was obtained by estimating σ as an inverse function of the lake's hydraulic retention time. Although this mass balance approach explained 84% of the variability in log–log transformed data, the prediction error for individual lakes was quite high. 5. Estimating σ as the ratio of a putative particle settling velocity to the mean lake depth yielded poorer predictions of lake TP ( r2 = 0.77) than the approach described above, and in fact did not improve model performance compared with simply assuming that σ is a constant for all lakes. 6. Our results also demonstrate that changing the flow-weighted input concentration should always have a directly proportionate impact on lake phosphorus concentrations, provided the type of phosphorus loaded (e.g. dissolved or particulate) does not vary. [ABSTRACT FROM AUTHOR]

Liquid crystalline elastomers and polymers, which are able to undergo large, reversible deformations in response to an applied stimulus (including heat, pH, or electromagnetic radiation) could potentially be useful in a variety of microactuator devices. However, in order to compete with traditional silicon-based systems it is necessary to show that liquid crystalline polymers can be patterned with reduced dimensions without losing their functionality. In this article we investigate three different techniques which can be used to pattern liquid crystalline polymers on the micro- and nanoscale. These techniques are templating, photopatterning, and microtransfer printing. Advantages and disadvantages of each process are explored. [ABSTRACT FROM AUTHOR]

We developed a mechanistic model of nutrient, phytoplankton, zooplankton and fish interactions to test the effects of phytoplankton food quality for herbivorous zooplankton on planktonic food web processes. When phytoplankton food quality is high strong trophic cascades suppress phytoplankton biomass, the zooplankton can withstand intense zooplanktivory, and energy is efficiently transferred through the food web sustaining higher trophic level production. Low food quality results in trophic decoupling at the plant-animal interface, with phytoplankton biomass determined primarily by nutrient availability, zooplankton easily eliminated by fish predation, and poor energy transfer through the food web. At a given nutrient availability, food quality and zooplanktivory interact to determine zooplankton biomass which in turn determines algal biomass. High food quality resulted in intense zooplankton grazing which favored fast-growing phytoplankton taxa, whereas fish predation favored slow-growing phytoplankton. These results suggest algal food quality for herbivorous zooplankton can strongly influence the nature of aquatic food web dynamics, and can have profound effects on water quality and fisheries production. [ABSTRACT FROM AUTHOR]

The transfer of energy and nutrients from plants to animals is a key process in all ecosystems. In lakes, inefficient transfer of primary producer derived energy can result in low animal growth rates, accumulation of nuisance phytoplankton blooms and dissipation of energy from the ecosystem. Most research on carbon transfer efficiency in pelagic food webs has focused on either food quantity or food quality, with the latter considered separately as either elemental stoichiometry or biochemical composition. The natural occurrence and magnitude of these types of growth limitations and their combined effects on Daphnia, a keystone grazer in pelagic freshwater ecosystems, are largely unknown. Our empirical models predict that the strength and nature of food quantity and quality limitation varies greatly with lake trophic state (total phosphorus, TP) and that Daphnia growth rates and thus energy and nutrient transfer efficiency are highest in lakes with intermediate trophic status (TP 10–25 μg l−1). We predict that food availability place the greatest constraint on Daphnia growth in nutrient poor lakes (TP≤4 μg l−1). Phosphorus limitation of Daphnia growth increased with decreasing TP, but the overall effect was never predicted to be the dominant constraining factor. Eicosapentaenoic acid (EPA, 20:5ω3) limitation was predicted to occur in both nutrient poor and nutrient rich lakes and placed the primary constraint on food quality in the most productive lakes. Two contrasting EPA-models gave different results on the magnitude of EPA-limitation, implying that additional food quality factors decrease Daphnia growth at high TP. In conclusion, the model predicts that Daphnia growth should peak in mesotrophic lakes, food quantity will place the greatest constraint on growth in oligotrophic lakes and EPA will primarily limit growth in eutrophic lakes. [ABSTRACT FROM AUTHOR]

Abstract: Using total phosphorus concentrations to estimate eutrophication risk is problematic for management purposes, as only some forms of phosphorus are biologically available for phytoplankton growth. This study estimated the bioavailability of particulate phosphorus, in forested, urban, agricultural (i.e. dairy farm) and mixed land cover streams. Sixteen stream sites were sampled during base and storm flow conditions and the following parameters were determined: total suspended solids, total phosphorus, total dissolved phosphorus, particulate phosphorus, percent bioavailable particulate phosphorus (%BAPP), total bioavailable phosphorus and sediment particle size distribution. Algal assays with Pseudokirchneriella subcapitata were used to measure %BAPP. Percent BAPP averaged 17%, 26% and 24% for streams draining catchments with forested, mixed use and agricultural land cover, respectively, and %BAPP did not vary significantly between base and storm flow conditions in these stream types. In contrast, %BAPP averaged 73% in the urban streams during baseflows but declined to an average of only 19% during storms. Particle size distributions did not correlate with %BAPP in these samples. During storm events, particulate phosphorus concentrations increased in all streams by an average of 614% and total phosphorus increased by 200%, whereas total BAP (i.e. total dissolved phosphorus+%BAPP×particulate phosphorus) only increased by 72% because on average only 20% of the particulate phosphorus transported during these events was biologically available. [Copyright &y& Elsevier]

Abstract: We developed a complex eutrophication model to simulate the current chemical and biological properties of Lake Washington (USA). The model reproduces the key epilimnetic and hypolimnetic temporal patterns of the system and results in a good fit between simulated and observed monthly values. The relative error of model estimates was below 20% for most of the water quality parameters (phytoplankton, phosphate, total phosphorus, total nitrogen, dissolved oxygen). Discrepancies between simulated and observed ammonium levels were mainly due to the explicitly modeled egestion of excess nitrogen during zooplankton feeding. This indicates that the relation between secondary production and nutrient recycling has significant effects on the fractionation of the major elements (C, N and P) and regulates their distribution between the particulate/dissolved and inorganic/organic pools. The model was forced by 1962 nutrient loadings, when the lake received large quantities of treated wastewater treatment effluent, and accurately predicted the phytoplankton community responses (phytoplankton biomass and cyanobacteria dominance) and the nitrogen and phosphorus annual cycles for these conditions. We used Monte Carlo simulations to reproduce the meteorological forcing (air temperature, solar radiation, precipitation and subsequent river inflows) that in large part regulates phytoplankton interannual variability for the last 25 years in the lake. We found three seasonal components (modes of variability). The first component (January, May, November, December) is associated with the conditions that determine the abundance of the herbivorous cladocerans; the second component (June–September) coincides with the summer-stratified period, and the third component (February–April) is associated with the initiation and peak of the spring bloom. Finally, an illustrative application of two scenarios of nutrient loading increase at 25% of the 1962 levels indicated that both phytoplankton and cyanobacteria growth are likely to be stimulated. The three seasonal components still characterize phytoplankton dynamics, but changes in the relationships between summer phytoplankton/cyanobacteria biomass and total phosphorus/phosphate concentrations indicate the likelihood of structural shifts towards relaxation of the present phosphorus-limiting conditions and promotion of cyanobacteria dominance. Integration of the present eutrophication model with a hydrodynamic model with enhanced vertical resolution will allow more realistic predictions. [Copyright &y& Elsevier]

Abstract: Complex environmental models are often criticized as being difficult to analyze and poorly identifiable due to their nonlinearities and/or their large number of parameters relative to data availability. Others consider overparameterized models to be useful, especially for predicting system dynamics beyond the conditions for which the model was calibrated. In this paper, we present a complex eutrophication model that has been developed to simulate plankton dynamics in Lake Washington, USA. Because this model is to be used for testing alternative managerial schemes, the inclusion of multiple elemental cycles (org. C, N, P, Si, O) and multiple functional phytoplankton (diatoms, green algae and cyanobacteria) and zooplankton (copepods and cladocerans) groups was deemed necessary. The model also takes into account recent advances in stoichiometric nutrient recycling theory, and the zooplankton grazing term was reformulated to include algal food quality effects on zooplankton assimilation efficiency. The physical structure of the model is simple and consists of two spatial compartments representing the lake epilimnion and hypolimnion. Global sensitivity analysis showed background light attenuation, the maximum phytoplankton growth rate, the phytoplankton basal metabolic rate, the zooplankton maximum grazing rate and the grazing half saturation constant have the greatest impact on model behavior. Phytoplankton phosphorus stoichiometry (maximum and minimum internal concentrations, maximum uptake rate) interacts with these parameters and determines the plankton dynamics (epilimnetic and hypolimnetic phytoplankton biomass, proportion of cyanobacteria and total zooplankton biomass). Sensitivity analysis of the model forcing functions indicated the importance of both external and internal loading for simulating epilimnetic and hypolimnetic plankton dynamics. These results will be used to calibrate the model, to reproduce present chemical and biological properties of Lake Washington and to test this lake''s potential response to different external nutrient loading scenarios. [Copyright &y& Elsevier]

Correlations which are artifacts of various types of data transformations can be said to be spurious. This study considers four common types of analyses where the X and Y variables are not independent; these include regressions of the form X/Z vs Y/Z, X × Z vs Y × Z, X vs Y/X, and X+Y vs Y. These analyses were carried out using a series of Monte Carlo simulations while varying sample size and sample variability. The impact of disparities in variability between the shared and non-shared terms and measurement error for the shared term on the magnitude of the spurious correlations was also considered. The accuracy of equations previously derived to predict the magnitude of spurious correlations was also assessed. These results show the risk of producing spurious correlations when analyzing non-independent variables is very large. Spurious correlations occurred in all cases assessed, the mean spurious coefficient of determination (r²) frequently exceeded 0.50, and in some cases the 90% confidence interval for these simulations included all large r² values. The magnitude of spurious correlations was sensitive to differences in the variability of the shared and non-shared terms, with large spurious correlations obtained when the variability for the shared term was larger. Sample size had only a modest impact on the magnitude of spurious correlations. When measurement error for the shared variable was smaller than one half the coefficient of variation for that variable, which is generally the case, the measurement error did not generate large spurious correlations. The equations available to predict expected spurious correlations provided accurate predictions for the case of X × Z vs Y × Z, variable predictions for the case of X vs Y/X, and poor predictions for most cases of X/Z vs Y/Z, and X+Y vs Y. [ABSTRACT FROM AUTHOR]

Determining the factors that control food web interactions is a key issue in ecology. The empirical relationship between nutrient loading (total phosphorus) and phytoplankton standing stock (chlorophyll a) in lakes was described about 30 years ago and is central for managing surface water quality. The efficiency with which biomass and energy are transferred through the food web and sustain the production of higher trophic levels (such as fish) declines with nutrient loading and system productivity, but the underlying mechanisms are poorly understood. Here we show that in seston (fine particles in water) during summer, specific ?3-polyunsaturated fatty acids (?3-PUFAs), which are important for zooplankton, are significantly correlated to the trophic status of the lake. The ?3-PUFAs octadecatetraenoic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid, but not a-linolenic acid, decrease on a double-logarithmic scale with increasing total phosphorus. By combining the empirical relationship between EPA-to-carbon content and total phosphorus with functional models relating EPA-to-carbon content to the growth and egg production of daphnids, we predict secondary production for this key consumer. Thus, the decreasing efficiency in energy transfer with increasing lake productivity can be explained by differences in ?3-PUFA-associated food quality at the plant-animal interface. [ABSTRACT FROM AUTHOR]

We conducted a statistical analysis of a long-term (1964-1998) record of intra- and interannual temperature fluctuations in Lake Washington, Washington. Lake Washington has experienced a warming trend, with overall increases of 1.5 (0.045°C yr[sup-1]) and 0.9°C (0.026°C yr[sup-1]), respectively, for temperature data weighted over the surface (0-10 m) and entire lake volume. This warming trend was greatest for the period from April to September and was smallest and nonsignificant for November-February. A principal-components analysis of the long-term mean monthly temperature time series identified two independent modes of interannual variability. The first mode represented the months of the year when the lake warms and is warmest (e.g., March-October) and explained 54% of the variability in the overall time series. The second mode represented the months when the lake cools and is coldest (November-February) and explained 24% of the variability. The March-October mode was positively correlated with interannual variability in air temperatures and the Pacific Decadal Oscillation (PDO), multivariate r² = 0.65. The November-February mode was positively correlated with air temperature, PDO, relative humidity, solar radiation, and wind speed (r² = 0.83). A heat budget model indicated that long-term trends had a secondary role and interannual variability dominated, with exceptions being net long-wave atmospheric radiation and surface-emitted radiation, for which the long-term trend explained ∼25% and 53% of the total variance, respectively. An increase in incoming long-wave radiation fluxes was mainly associated with the increase in minimum daily temperatures (0.06°C yr[sup-1], r² = 0.47), especially during the March-October mode, when the linear trend accounted for 85% of the variability. [ABSTRACT FROM AUTHOR]

We conducted a series of experiments using the herbivorous zooplankter Daphnia pulex to investigate the nutritional importance of dietary polyunsaturated fatty acids (PUFAs). Daphnia were fed three different diets: (1) a PUFA-deficient cyanophyte mixture, (2) a cyanophyte mixture with fatty acid (FA) amendments, or (3) a PUFA-rich cryptophyte mixture. We devised a novel method using customized phosphatidylcholine liposomes to deliver specific FA amendments in a pure and bioavailable form that closely mimics their form in natural diets. We added FA-impregnated liposomes to the cyanophyte mixtures at levels equivalent to the observed differences in FA concentrations between the cyanophyte and cryptophyte mixtures. Liposome control amendments (without FAs added) had no effect on Daphnia growth. Eicosapentaenoic acid (EPA)-impregnated liposome amendments accounted for 30% of Daphnia somatic growth-rate differences and 38% of clutch-size differences between the cyanophyte and cryptophyte diets. Liposome supplementation of a FA mixture, which included a saturated fatty acid and the four ω3 PUFAs most prevalent in cryptophytes but rare in cyanophytes, accounted for 59% of Daphnia somatic growth-rate differences and 47% of clutch-size differences between the cyanophyte and cryptophyte diets. Our study suggests that phytoplankton ω3 PUFA, and especially EPA, content plays an important direct role in herbivorous zooplankton nutrition. [ABSTRACT FROM AUTHOR]

Features a study that tested the hypothesis that sockeye salmon in Lake Washington, Washington experience growth limitation because of content of phosphorus or specific essential fatty acids in their diet. Equations and parameter values for the bioenergetics model; Potential for food quality limitation of growth; Ratios of phosphorus to carbon for both sockeye salmon and zooplankton.

1. A series of experiments examined growth of Daphnia magna on three algal diets ( Rhodomonas minuta , Scenedesmus acutus and Synechococcus sp.) at varying physiological states [nitrogen and phosphorus (P) limitations] to test whether variation in algal fatty acid and/or elemental composition can predict Daphnia growth. 2. These algae differed widely in their essential fatty acid (EFA) composition while phosphorus (P) or nitrogen limitation had only a small influence on their ω3-polyunsaturated fatty acid (PUFA) content. 3. Individually, algal ω3-PUFA content explained 69% of the variation in the normalised growth of D. magna, while algal phosphorus content explained 11% of the variation. Quantitative models for D. magna growth used both algal ω3-PUFA content and algal C : P ratio as food quality indices. Together, algal ω3-PUFA content and C : P ratio explained 70% of the variation in the normalised growth rate of D. magna . 4. Our results indicate that EFA influenced algal food quality much more strongly than P. The EFA and mineral P impacts appear to be independent. [ABSTRACT FROM AUTHOR]

Offers the results of a study on the role of eicosapentaenoic acid content. Importance the essential fatty acid on zooplankton growth and egg production; Impact of the accumulation of phytoplankton biomass that results in water quality deterioration due to low transfer efficiencies; Explanation of the reason why the relationship between plants and animals and consumer interface is the least predictable link in aquatic ecosystems.

1. Polyunsaturated fatty acids (PUFA) are almost exclusively synthesized by plants. Animals can convert from one form of PUFA to another through elongation and desaturation, but very few can synthesize PUFA de novo. PUFA play an important role in regulating cell membrane properties, serve as precursors for important animal hormones and are essential for animals. 2. In aquaculture studies, highly unsaturated fatty acids (HUFA), a subset of PUFA, have been found to be critical for maintaining high growth, survival and reproductive rates and high food conversion efficiencies for a wide variety of marine and freshwater organisms. 3. The plankton literature suggests high food-quality algae species are rich in HUFA and low food-quality algae are poor in HUFA. Adding semi-pure emulsions of HUFA to algae monocultures can markedly increase the growth rates of zooplankton feeding on these mixtures. 4. A study measuring zooplankton biomass accrual when feeding on natural phytoplankton found a strong correlation between phytoplankton HUFA (specifically eicosapentaenoic acid) content and herbivorous zooplankton production. 5. The aquatic ecology literature suggests that planktonic foodwebs with high HUFA content phytoplankton have high zooplankton to phytoplankton biomass ratios, while systems with low HUFA phytoplankton have low zooplankton biomass. Also, the seasonal succession of plankton in many temperate lakes follows patterns tied to phytoplankton HUFA content, with intense zooplankton grazing and 'clear-waterphases' characteristic of periods when the phytoplankton is dominated by HUFA-rich species. 6. Herbivorous zooplankton production is constrained by the zooplankton's ability to ingest and digest phytoplankton. It is becoming increasingly clear, however, that much of the phytoplankton which is assimilated may be nutritionally inadequate. HUFA may be key nutritional constituents of zooplankton diets, and may determine energetic efficiency across the plant-animal interface, secondary production and the strength of trophic coupling in aquatic pelagic foodwebs. [ABSTRACT FROM AUTHOR]

Discusses advanced process simulation of metal film deposition. Film growth simulation; Collimated sputtering; Wafer-scale uniformity; Hot aluminum deposition; Metallization problems.

Presents a meta-analysis of the trophic cascade in freshwater food webs. Weak support for the idea that manipulations of fish communities can be used to consistently control algal biomass in lakes.

Examines the English-language literature on Algeria generated by the Algerian war of independence. Looking at the Algerian situation from British and North American points of view; Algerian war of independence as the great transformer of a colonial into a national society; Theory of radical anti-colonial revolution; Class factor and terrorism in the fight for independence.

Reflectivity of a photonic crystal device fabricated by glancing angle deposition may be reversibly altered by infiltration with an absorbing dye solution. An electric field controls the dye ion motion through the photonic crystal. Rapid reflectance changes up to 0.4 in the crystal’s optical band gap are demonstrated. The time evolution of the dye movement process is examined and its operation described. This work may have applications for a passive optical display. [ABSTRACT FROM AUTHOR]

This study examined the physical, chemical and biological characteristics of the phosphorus (P) in the effluents from a paper processing facility before and after an alum based P removal process. The alum based treatment process reduced effluent total P concentrations from an average of 230 ± 103 (±1 SD) μg L−1 to an average of 36 ± 10 μg L−1. Ultra-filtration showed the treatment process shifted the P in these effluents from being 75 ± 9% particulate pre-removal to being 52 ± 0% dissolved and 27 ± 1% colloidal after the Trident P removal process. The alum removal process also reduced the fraction of reactive P in the dissolved and colloidal pools from 55% to 14%, respectively. Algal phosphorus bioavailability (BAP) bioassays showed the BAP of these effluents averaged 12 ± 9% of total P. Algal dissolved P uptake experiments indicated ≈ 30% of the dissolved P was converted to particulate P (which usually indicates algal uptake) during 21-day bioassays. However, treatments without algae indicated >80% of the apparent algal uptake may have been due to colloidal P forming flocs via physical-chemical processes. These analyses indicate the phosphorus contained in this paper processing facility's effluents had much lower bioavailability than the P in typical municipal wastewater treatment plant effluents. Unlabelled Image • Alum based technology was effective in treating paper processing facility effluent. • P in the effluent from paper processing facility had very low bioavailability. • Most of the P in the paper mill effluents tested was humic bound. • P uptake in bioassay experiment was mainly due to physical-chemical processes. [ABSTRACT FROM AUTHOR]

Presents information on factors influencing the food web structure. How information was obtained; Predictions made on the food web structure; What are considered classic experimental devices for studies of planktonic ecosystems; Analysis of data collected on the food web structure.